1. Technical Field
This Application claims the benefit of People's Republic of China Application No. 201010204628.5, filed Jun. 12, 2010.
The present invention generally relates to touch sensing technology, and more particularly to a touch sensing, circuit for a capacitive touch panel and a method for making the circuit.
2. Description of the Prior Art
In recent years, the touch panel is becoming more and more popular, and may replace mouse and keyboard in the future. Touch panels have been widely used in home appliances, communication devices, and electronic information products such as personal digital assistant (PDA), and game input interface. Now, a touch panel is always integrated with a display panel, so a user can select an operation by directly touching the corresponding images shown, on the display panel. Therefore, such a combined structure of the touch panel and the display panel provides users with better portability and more comfortable input operation.
There are many types of touch panels, such as resistance touch panel, capacitive touch panel, infrared sensing touch panel, electromagnetic sensing touch panel, and acoustic wave sensing touch panel, according to different technology principles. Herein, the capacitive touch panel is a comparatively better type because of its high sensitivity, low cost, and simple structure. Theoretically, the capacitive touch panel detects the capacitance changes of the electrodes generated by human body or other grounded material to determine the touch position.
Referring to FIG. 1, a conventional capacitive touch panel includes a sensing circuit pattern, made of conductive materials and formed on a transparent glass. The circuit pattern has x-axis (X0-X7) and Y-axis (Y0-Y4) electrode strips. In operation, a control circuit scans the electrode strips sequentially. When a human finger or other grounded conductors touch a point (shown as black area) of the capacitive touch panel, the capacitance of the X-axis electrode strips and Y-axis electrode strips which is touched changes. After sensing the capacitance change of the electrode strips, the control circuit will determine the X-axis and Y-axis coordinates of the touched position based on the capacitance changes.
As is well known, to detect the location touched by finger or touch pen, various touch detection methods for capacitive touch panels have been employed. For example, as shown in FIG. 2, a touch sensing circuit 201 having a grid pattern for a capacitive touch panel formed on a substrate 205 includes a first capacitive sensing layer 202, a second capacitive sensing layer 203, and an insulating layer 204. The first capacitive sensing layer 202 and the second capacitive sensing layer 203 are spaced by the insulation layer 204 so as to achieve an effect of capacity. Each capacitive sensing layer includes a number of conductive elements arranged in substantially parallel rows. The conductive elements of the first capacitive sensing layers are perpendicular to the conductive elements of the second capacitive sensing layer. Each conductive element includes a number of electrode units. The conductive elements are made of indium tin oxide (ITO).
However, the above mentioned touch sensing circuit has two sensing layer 202 and 203 which make the structure thick. Furthermore, the conductive elements are made of indium tin oxide, therefore the whole resistance of the touch sensing circuit can not be reduced effectively. Consequently, a sensitivity of signal transmission can not be enhanced.
Therefore, a new touch sensing circuit having not only a comparatively thinner structure but also a comparatively lower impedance is needed to overcome said shortcomings.